The construction sector is responsible for substantial energy consumption, greenhouse gas emissions, and resource depletion, driving the search for sustainable alternatives to conventional petroleum-based insulation materials. Lignocellulosic biomass, comprising cellulose, hemicellulose, and lignin, offers a renewable resource for the development of bio-based foams with potential application in construction systems. This review provides a comprehensive analysis of bio-based foams tailored to building applications, positioning recent scientific advances against the technical properties of commercial synthetic insulation foams. Key performance parameters, including density, thermal conductivity, compressive strength, dimensional stability, water vapour diffusion resistance, and fire behaviour, are critically examined. Developments in lignocellulosic-based foams are discussed, highlighting processing strategies such as crosslinking, chemical modification, and hybrid reinforcement to enhance mechanical, thermal, and fire performance. The reported results demonstrate that lignin-based polyurethane and phenolic foams can achieve competitive compressive strength and thermal insulation, while cellulose-based aerogels and foams exhibit ultra-low density and promising conductivity values. However, challenges related to moisture sensitivity, fire classification, process scalability, standardisation, and market integration remain significant. Overall, lignocellulosic foams represent a promising pathway toward decarbonised, circular construction systems, provided that technical optimisation and regulatory alignment are successfully achieved.

Research on tannin-based foams has shown promising results. However, all developments in this field have not been addressed from different perspectives, in a systematic way, and with an emphasis on sustainability. This work discusses different formulations, emphasizing their bio-based components and how modifications influence key properties. It examines life cycle assessment (LCA) studies through a sustainability lens and identifies major commercial phenolic products to highlight the practical use of tannin foams for thermal insulation. The type of tannins, as well as their sources, influences the key properties of these foams. The replacement of formaldehyde, a crosslinking agent known for its health risks, is possible, particularly through more sustainable alternatives that allow for foams with better properties than those obtained with formaldehyde. Substitution of diethyl ether with less hazardous alternatives results in foams with improved thermal and mechanical performance. The elimination of the blowing agent—the green alternative—also leads to foams with good performance. The presence of additives (surfactants, plasticizers, and fillers), some of which are sustainable, improves the mechanical properties of the foams. The performance in fire-related applications, already promising, is also enhanced by the presence of additives. An increase in understanding, combined with the sustainable nature of the various alternatives, makes tannin-based foams promising candidates for next-generation insulation and structural materials in construction.

Nature offers a robust conceptual framework for designing next-generation adaptive, multifunctional sensing systems. Also, in sensing systems, Trojan materials add a functional dimension to the microstructure, enabling the development of high-performance humidity sensors without interfering with their macrostructure. Thus, based on a brief overview of how inspiration from plants, animals, and membranes can be used to engineer high-performance platforms for environmental humidity monitoring, combined with the functional dimension of Trojan materials, this review presents a critical framework detailing the key developments in the main categories of self-sensing materials within the scope of humidity sensors. The review addresses electronically and ionically conductive polymers, polymer composites with dispersed active fillers, and hydrogel-based or other water-compatible systems. Additionally, commercially available sensors are described, and the main challenges and future directions are identified.